Define nitrogen estimation - kjeldahl''s method, Biology

Assignment Help:

Define Nitrogen Estimation - Kjeldahl's Method?

Nitrogen in the protein is estimated by a method referred to as Kjeldahl's method. Although over a period of time many other methods have emerged for determination of organic nitrogen, this method still remains an old favourite because it is reliable and has very well standardized procedures. The method involves the digestion of the weighed sample with concentrated sulphuric acid, selenium oxide, potassuim sulphate and copper sulphate in a long necked special digestion flask known as kjeldahl's flask. Potassium sulphate increases the boiling point of the mixture. Since the digestion results in fuming of the sulphuric acid, the procedure has to be carried out in a fume hood and the procedure takes several hours. The sample is digested until the solution in the digestion flask becomes clear after which it is transferred to an appropriate volumetric flask (usually 50 or 100 ml flask) and the volume is made up to the mark with distilled water. Aliquots of this sample are used for distillation in the kjeldahl's apparatus and nitrogen in the protein is estimated. Most proteins contains 16% nitrogen. Thus, percent nitrogen content is multiplied by 6.25 to get crude protein content.

1805_Nitrogen Estimation - Kjeldahl’s Method.png

The experiment involves decomposition of ammonium sulphate by a fixed volume of alkali (NaOH). Ammonium sulphate on decomposition releases ammonia which is collected in a flask of boric acid solution Tashiro's indicator. With boric acid ammonia forms a complex 'ammoium borate'. As ammonia is distilled into the boric acid, the Tashiro indicator slowly changes colour from pink to green. This is because the colour of the indicator is pH dependent - it is pink in acidic medium and green in alkaline medium. When the green coloured solution containing the boric-acid-ammonia complex is retitrated against H2SO4, the solution slowly becomes acidic again and the indicator becomes pink. This point when colour changes from green to pink is taken as the end point.


Related Discussions:- Define nitrogen estimation - kjeldahl''s method

Which type of gamete do the male respectively produce, Concerning the sex c...

Concerning the sex chromosomes of the XY system which type of gamete do the male and the female individuals respectively produce? The individual of the male sex is XY so he for

Mathematical and statistical challenges, Progress on these biological issue...

Progress on these biological issues needs both that more mathematics and statistics be brought to bear on them and that new mathematical and statistical tools be prepared. All the

How old is the earth, How old is the earth? It is believed that the ear...

How old is the earth? It is believed that the earth is about 4.5 billion years old.

Homoeostasis, what stimulate the system in homoeostasis

what stimulate the system in homoeostasis

All part., Wat type of animal is tick and weevil?

Wat type of animal is tick and weevil?

Explain properties related to protein-protein interactions, Explain Propert...

Explain Properties related to protein-protein interactions? Properties related to protein-protein interactions include dough formation, one of the important functional properti

Chemical energy to be used by the living beings on earth, Q. How is the lig...

Q. How is the light from the sun transformed into chemical energy to be used by the living beings on earth? Light from the sun is converting into chemical energy contained in o

RNA synthesis, Distinguish features in the mechanisms of RNA synthesis, + (...

Distinguish features in the mechanisms of RNA synthesis, + (RNA), (-) RNA, and ds RNA viruses.

Corpus cardiacum - endocrine organs, Corpus Cardiacum - Endocrine Organs ...

Corpus Cardiacum - Endocrine Organs We before mentioned that corpus cardiacum (pl. corpora cardiaca) is a neurohemal organ in insects. It is gland of neural origin. They are c

Explain adverse effects of bronchospasm, Adverse Effects of Bronchospasm ...

Adverse Effects of Bronchospasm Nasal and throat discomfort can occur. Bronchospasm, sometimes severe, has been reported uncommonly in patients with reactive airway disease; za

Write Your Message!

Captcha
Free Assignment Quote

Assured A++ Grade

Get guaranteed satisfaction & time on delivery in every assignment order you paid with us! We ensure premium quality solution document along with free turntin report!

All rights reserved! Copyrights ©2019-2020 ExpertsMind IT Educational Pvt Ltd